A Strategy for Selective Catalytic B–H Functionalization of o-Carboranes

Accounts of Chemical Research, Journal Year: 2021, Volume and Issue: 54(21), P. 4065 - 4079

Published: Oct. 24, 2021

ConspectusCarboranes are a class of polyhedral carbon-boron molecular clusters featuring three-dimensional aromaticity, which often considered as 3D analogues benzene. Their unique structural and electronic properties make them invaluable building blocks for applications ranging from functional materials to versatile ligands pharmaceuticals. Thus, selective functionalization carboranes has received tremendous research interest. In earlier days, the vast majority works in this area were focused on cage carbon via facile deprotonation CH, followed by reaction with electrophiles. On contrary, B-H activation is very challenging since 10 bonds o-carborane similar, how achieve desired transformation at specific boron vertex long-standing issue.As more electronegative than boron, property results different charges cage, follow order B(3,6)-H ≪ B(4,5,7,11)-H < B(8,10)-H B(9,12)-H. We thought that difference may trigger favorite interaction proper transition metal complex bond carborane, could be utilized solve selectivity issue. Accordingly, our strategy described follows: (1) electron-rich catalysts good most electron-deficient (connected both C-H vertices); (2) relatively B(8,9,10,12)-H (with no bonding either (3) directing-group-assisted catalysis appropriate only one vertex), whose lie middle range bonds. This been successfully applied laboratory other groups development series synthetic routes catalytic carborane resulting synthesis large number cage-boron-functionalized derivatives regioselective fashion. Subsequently, significant progress emerging made.In 2013 we reported tetrafluorination o-carboranes using an Pd(II) salt, [Pd(MeCN)4][BF4], catalyst. 2014 disclosed first example carboxy-directed alkenylation B(4) promoted Ir(III) 2017 presented Ir(I)-catalyzed diborylation also uncovered Pd-catalyzed asymmetric chiral-at-cage 2018. These proof-of-principle studies have greatly stimulated activities enabled catalysts. so far developed toolbox methods B-olefination, -arylation, -alkenylation, -alkynylation, -oxygenation, -sulfenylation, -borylation, -halogenation, -amination. recently expanded base catalysis. As field progresses, expect will invented, detailed Account promote these efforts.

Language: Английский

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Organocatalytic Asymmetric Synthesis of o-Carboranyl Amines

Journal of the American Chemical Society, Journal Year: 2025, Volume and Issue: unknown

Published: Jan. 14, 2025

Carboranyl amines are distinct from typical organic amines. Due to the electronic influence of carborane cage, they have low nucleophilicity and reluctant alkylate. Moreover, asymmetric synthesis chiral carboranes is still in its infancy. Herein we achieved first catalytic N-alkylation o-carboranyl amine, providing general access diverse secondary with high efficiency enantioselectivity under mild conditions. For time, organocatalysis was introduced chemistry. Key success use situ generated (naphtho-)quinone methides as alkylating reagents suitable acid catalysts. This protocol also applicable S-alkylation 1-SH-o-C2B10H11. Control experiments kinetic studies provided important insights into reaction mechanism, which likely involves rate-determining generation quinone methide followed by fast enantio-determining nucleophilic addition.

Language: Английский

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Recent Advances in Transition Metal-Catalyzed Selective B-H Functionalization ofo-Carboranes

Bulletin of the Chemical Society of Japan, Journal Year: 2020, Volume and Issue: 94(3), P. 879 - 899

Published: Dec. 18, 2020

Abstract Carboranes are a class of carbon-boron molecular clusters, possessing extraordinary characteristics including three-dimensional aromaticity conjugated by σ-bonds, icosahedral geometry and inherent robustness. They finding growing applications as valuable building blocks in boron neutron capture therapy agents, pharmacophores, nanomaterials, optoelectronic, organometallic/coordination chemistry more. Therefore, the effective controlled functionalization carboranes has attracted enormous research interests, particularly regio- enantio-selective cage BH derivatization among ten chemically similar vertices o-carboranes. Only recent few years, significant progress been made transition metal catalyzed vertex-specific functionalization. This review summarizes advances this realm.

Language: Английский

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Iridium-Catalyzed Cyclative Indenylation and Dienylation through Sequential B(4)–C Bond Formation, Cyclization, and Elimination from o-Carboranes and Propargyl Alcohols

Journal of the American Chemical Society, Journal Year: 2020, Volume and Issue: 142(22), P. 9890 - 9895

Published: May 12, 2020

Described herein is the first iridium-catalyzed cyclative indenylation through sequential B(4)–C and intramolecular C–C bond formation from o-carboranes propargyl alcohols, leading to of B(4)-indenylated with excellent regioselectivity via direct B–H activation. Moreover, regioselective 1,3-dienylation has been accessed activation, dehydration, decarboxylation, producing B(4)-dienylated o-carboranes.

Language: Английский

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Copper-Catalyzed Electrochemical Selective B–H Oxygenation of o-Carboranes at Room Temperature

Journal of the American Chemical Society, Journal Year: 2020, Volume and Issue: 142(15), P. 6940 - 6945

Published: March 31, 2020

Copper-catalyzed electrochemical selective cage B–H oxygenation of o-carboranes has been achieved for the first time. Under a constant electric current (4.0 mA) at room temperature, copper-catalyzed cross-coupling carboranyl amides with lithium phenolates results in formation B(4,5)-diphenolated via direct activation, whereas use tert-butoxide affords B(4)-monooxygenated products. This reaction does not require any additional chemical oxidants and generates H2 salt as byproducts. Control experiments indicated that high-valent Cu(III) species is likely involved process.

Language: Английский

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Pd‐Catalyzed Selective Bifunctionalization of 3‐Iodo‐o‐Carborane by Pd Migration

Angewandte Chemie International Edition, Journal Year: 2019, Volume and Issue: 59(12), P. 4851 - 4855

Published: Dec. 25, 2019

Abstract A palladium‐catalyzed highly selective 3,4‐bifunctionalization of 3‐I‐ o ‐carborane has been developed, leading to the preparation 3‐alkenyl‐4‐R‐ ‐carboranes (R=alkyl, alkynyl, aryl, allyl, CN, and amido) in high excellent yields. This protocol combines sequential activation cage B(3)−I B(4)−H bonds by Pd migration from exo ‐alkenyl sp 2 C B(4), which is driven thermodynamic force. represents a brand‐new strategy for bifunctionalization carboranes with two different substituents.

Language: Английский

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Regioselective B(3,4)–H arylation of o-carboranes by weak amide coordination at room temperature

Chemical Science, Journal Year: 2020, Volume and Issue: 11(39), P. 10764 - 10769

Published: Jan. 1, 2020

B–H: site-selective B(3,4)–H arylations were accomplished at room temperature by versatile palladium catalysis enabled weakly coordinating amides.

Language: Английский

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Ir-Catalyzed Selective B(3)-H Amination of o-Carboranes with NH₃

Journal of the American Chemical Society, Journal Year: 2021, Volume and Issue: 143(11), P. 4148 - 4153

Published: March 15, 2021

Ammonia gas, NH3, is a cheap and widely used industrial feedstock, which has received tremendous research interests in its functionalization. This work reports breakthrough catalytic selective cage B(3)-H amination of o-carboranes with NH3 via Ir-catalyzed B-H/N-H dehydrocoupling, offering convenient efficient access to series 3-NH2-o-carborane derivatives moderate high isolated yields broad substrate scope. The employment readily available gas as the aminating reagent H2 sole byproduct endows protocol economy, practicability, environmental friendliness. A plausible reaction mechanism proposed on basis control experiments.

Language: Английский

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Electrochemical Cage Activation of Carboranes

Angewandte Chemie International Edition, Journal Year: 2022, Volume and Issue: 61(20)

Published: Feb. 11, 2022

Abstract Carboranes are boron–carbon molecular clusters that possess unique properties, such as their icosahedron geometry, high boron content, and delocalized three‐dimensional aromaticity. These features render carboranes valuable building blocks for applications in supramolecular design, nanomaterials, optoelectronics, organometallic coordination chemistry, neutron capture therapy (BNCT) agents. Despite tremendous progress this field, stoichiometric chemical redox reagents largely required the oxidative activation of carborane cages. In context, electrosyntheses represent an alternative strategy more sustainable syntheses. It is only recent few years considerable has been made electrochemical cage functionalization carboranes, which summarized Minireview. We anticipate electrocatalysis will serve increasingly powerful stimulus within current renaissance electrochemistry.

Language: Английский

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One‐Pot Process to Carborano‐Coumarin via Catalytic CascadeDehydrogenative Cross‐Coupling

Chinese Journal of Chemistry, Journal Year: 2020, Volume and Issue: 38(4), P. 383 - 388

Published: Jan. 16, 2020

Summary of main observation and conclusion Ir‐catalyzed cascade dehydrogenative CH/BH BH/OH cross‐coupling carboranyl carboxylic acid with readily available benzoic has been achieved, leading to the facile synthesis previously unavailable carborano‐coumarin in a simple one‐pot process. Two cage B—H, one aryl C—H O—H bonds are activated construct efficiently new B—C B—O bonds. The cyclization can stop at first B—H/C—H step by tuning reaction conditions, resulting series α‐carboranyl carborane derivatives. Control experiments indicate that dehydrocoupling proceeds preferentially over B—H/O—H dehydrocoupling, both directing groups oxidants crucial for this reaction. An iridium(V) intermediate is proposed be involved catalytic cycle.

Language: Английский

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